Mostly deep-sea urchins found all over the world (many in greater than 1500 m depths-in NZ they range from 100 to 5000 m!), but with some shallow water relatives (aka the Fire urchins, I'll save these for another day)

They often have very sharp and poisonous spines. And yes, the deep-sea ones too...

They "walk" around on the sea bottom with special spines that have hoof like tips

They were described FIRST as fossils and the living animals were found AFTER...

When the animals are alive they look kind of like this:

An Atlantic species by Hankplank

On this purple species from the Pacific (Tromikosoma maybe? this isn't one of the new ones described by Anderson), you can see the white hoof-like spine tips that the urchins use to "walk" along the bottom..

Image by Neptune Canada

Here is a pic showing the oral surface (ie the bottom). The mouth is at center and as you can see it is surrounded by spines with those white "hoof" like tips. These are what the animals use to "walk" along the bottom of the sea floor.

As a result of this "deflated" appearance, they are often called a variety of names: "pancake urchin", "leather urchin", "bag urchin", or "beret urchin." However in Anderson's new paper he feels a new common sobriquet would be most accurate-the Tam O Shanter urchin!!!

Even alive, looking down on one, you can sort of see the resemblance..(note however this is not one of Anderson's new species)

Image by Neptune Canada!

Owen's paper (here) describes a whopping SEVEN species in two genera. That's pretty significant given that MOST of these urchins were described in the early part of the 20th Century/late 19th.

These were all discovered and described by looking at a variety of different characteristics. Some as straightforward as body color as well as spine shape and location. But some characteristics are more subtle. These are the individual pieces of pedicellariae-little claw like structures that are present on all sea urchins..which were studied using a Scanning Electron Microscope to yield distinct shapes...

Fig. 28 from Anderson 2013

He also reviewed the many echinothurioid urchins in the New Zealand waters, in addition to the seven known species, Anderson described/reviewed a further nine species (7 were new) culminating in a count of some 16 species of these urchins in the region!, including this beauty... Araeosoma thetidis!! (described by Hubert Lyman Clark in 1909)

Those pictures were close ups of asteroids from cold-water settings in the North Pacific & North Atlantic. There's a very different fauna of asteroids in those parts of the world compared to the tropics.

Most of the starfish in the tropical Indian and Pacific Oceans show a lot of granules, spination and armor and of course are composed of very different families of asteroids compared to those which live in the far North.

I start with the above : a STUNNING shot of Protoreaster nodosus, a commonly encountered sea star found throughout the Pacific. Shots below are macro shots showing skeletal features and colors of different tropical, Indo-Pacific starfish species.

More close up on Protoreaster with more pointed spines. Image by Nick Robertson Brown (Frogfish Photos)

What are these weird threads? Feeding tentacles from a benthic ctenophore? Gametes? Weird. Photo by MerMate (Eunice Khoo)

The strange soft-warty structures are a distinguishing feature on the surface of Echinaster callosus! Function unknown. Images by Optical Allusion

Some fantastic detail on the ophidiasterid Nardoa. Image by Stephane Bailliez

Here's a close up on Gomophia gomophia. Image by Okinawa Nature Photography (Shawn Miller)

An awesome close up of the disk on Fromia nodosa from the Maldives. Image by Philippe Guillaume.

Close up of Fromia indica. Image by Jesse Claggett

The papulae (aka the gills) and spines of Acanthaster planci-the Crown of Thorns starfish. Image by Barry Fackler.

This one shows a close up of the gills of Acanthaster planci. Image by David Garcia Fonseca.

Wow! First record of the brittle star Ophiactis? living on the spines of Pentaceraster. Image by Maractwin

another tight shot of a brittle star (Ophiothela?) living on the asteroid Nardoa. Image by deco4macro

The same kind of star sans ophiuroid. Image by samui13coconut13

Surface spines on Pentaceraster. The tiny white circles on the brown spaces are papulae aka the gills. Image by Friscodive.

]

Surface close up on the cushion star Culcita novaeguineae from the Maldives. Image by Frédérique Jaffeux. All the white pores are papulae aka the gills.

Tuesday, May 14, 2013

One of the things I love about biology is when you have an animal which has been studied down to the wire and become so familiar that people take it for granted, and then you discover something completely new about it!!!

And that in turn gives you insight into past events and other things around you. Cryptic? Yes..but I will explain.

It studies the reaction of the classic workhorse starfish Pisaster ochraceus as it reacts to one of the harshest of environmental stresses: the ocean itself! WAVES!! SPLOOSH!

Image by Lance and Erin Willett

Details....
Hayne and Palmer collected numerous individuals in and around Barkley Sound near the Bamfield Marine Sciences Center on Vancouver Island. Individuals were collected and measured to assess values for drag and lift. Some were tagged and returned to the field for various field transplant experiments (look below).

Specimens were also surveyed in the field and correlated with the power of various wave forces.

Their findings!

1. Sea stars in wave-exposed sites had narrower arms and were lighter per unit arm length than those from sheltered sites. On average, animals from the most exposed sites were 12% narrower at the base compared to the most sheltered!

2. Body form was tightly correlated with the maximum velocity of breaking waves across four different localities and over time.

3. Sea stars were transplanted between sheltered sites to more wave-exposed sites revealing that they became LIGHTER per unit arm length, developing narrower arms after 3 months! There was a tight correlation between water flow and the body shape which strongly supported the idea that wave force was affecting the body shape.

This figure 7 very nicely summarizes their findings. The animal on your left ("A") is an example of an animal from "most sheltered" going right to the one on the lower right from "most wave exposed".

and the small box "D" even shows the extent that the abactinal spine/granules show density and a heavier degree of calcification between a sheltered (orange on the left) vs. an exposed (purple on the right) individual.

The exposed form below is overall smaller in size, weigh less, and with a higher aspect ratio (arms narrower, etc.) and with a more dense skeleton. Dynamics
1. This is thought to aid the individuals in a wave-exposed environment from being washed away. Not as much lift and not as much drag.
2. The heavier granules offer more protection against the crashing forces of the waves.
3. BUT, having a higher aspect ratio comes with some costs:
a. such as being more prone to overheating. Sheltered are much more effective at resisting
overheating and water loss. Although heating may be offset by cooling temperatures from
waves and such..
b. having smaller areas available for gonads. This results in lower overall production of
reproductive material and so on..

Image by jkenning

Image by Shannon Robalino

The protected body form
These make more sense in protected areas away from the harsh, crashing wave-swept regions:
Some dynamics...

1. Larger animals are more likely to be caught and washed out to shore. (greater drag and lift at play)
2. BUT the larger, thicker size involves more water retention and thus better thermoregulation and better cooling.
3. Greater volume for gonads! More potential offspring!

from Scenic Beach State Park in Washington
From Samantha Russell

Bear in mind-that in order to test these interpretations, animals were actually transplanted between protected vs. wave-swept areas. Transplanted animals (from protected to the exposed wave-swept areas) decreased in mass and increased in aspect ratio over time. Environemntal factors directly affected the body shape of ochre stars!Biophysics Meets old fashioned Taxonomy!

Probably the neatest footnote to all of this was that these differences in different forms of Pisaster was observed by several naturalists in California, early in the 20th Century.

Fisher even observed that the differences in three of these forma seemed to be based on the degree of calcified skeleton, i.e., how built up the spines were...

It is difficult to escape the inference that the characteristic small spinelets of the abactinal area are correlated with queit water, but that this is ot the only factor is evidenced by the presence, along with confertus, of forma ochraceus and nodiferus, the latter found on open coasts and also in deep water (Monterey Bay).

The variant nodiferus is Hayne and Palmer's "exposed coast" morphological form. Fisher's comments about the inconsistency of abactinal spinelet shape/size suggest there remains even more variation and other factors to consider in future studies..

Sometimes, these "forma" turn out to be distinct taxa-perhaps subspecies or species. But sometimes its just some variation in body form in reaction to the environment.

Just as if we took a flabby, couch potato from his comfy TV room with silk bedsheets and put that person into an underground mine to dig minerals for a living. We would perhaps see changes in musculature, bone structure, and maybe even hair/eye color.

So there you have it! A cool convergence between a modern biophysics story with a fun footnote from classical taxonomy/natural history!
Are these considerations we might apply to other intertidal asteroids in similar settings? (Stichaster australis from New Zealand). Image by Jon Mollivan

Tuesday, May 7, 2013

Today, here in Washington DC, we have an overcast day with a rather dreary storm raining down on us..and a quick skim through the news is filled with all kinds of blah and bad news, Sequester is the buzz of the town.. so..meh. What to do??

FLATWORM COLOR EXPLOSION!!!!!

Pseudoceros susanae, in the Maldives by Jim Anderson

A brief zoology lesson: Flatworms are members of the phylum Platyhelminthes. This is the group of worms which includes many parasitic forms, such as the tape worms and trematodes as well as several free-living species that live on land, in freshwater and in the ocean.

If you remember those funny arrow-headed ones that you could cut and via regeneration give it two or more heads? That was a flatworm! Many, many species are found throughout the world.

Free living flatworms are mostly predatory-feeding on immovable animals, such as tunicates to other smaller animals and worms. There's a LOT of different species with many interesting biological stories! Some (go here) are mimics with nudibranchs!

But most folks don't realize just how colorful and gorgeous they are in the tropics! Here is a bunch....

Pseudoceros bifurcus from Kenya.

Photo by Jim Anderson

Another of the same species (P. bifurucs) from Singapore apparently feeding on some tunicates.

Photo by Wild Singapore

Pseudoceros laingensis from Straits of Johore

Photo by Arthur Anker

Sorry, this one didn't have a name.. Amazing to look at though... From French Polynesia.

Photo by Pauline Bosserelle

Another flatworm I don't have a name for.. but apparently from the Philippines

About Me

I pursue starfish related adventure around the world with a critical eye and an appreciation for weirdness.
Support has been courtesy of the National Science Foundation but the views and opinions presented herein are mine and do not reflect the opinions of them or any affiliated institutions.
Need to hire an invertebrate zoologist/marine biologist? Please contact me!